A panic exit device (or panic device) operates by employing an inward force on a push bar to unlatch a latching mechanism from a latch strike. Panic devices commonly incorporate a latching mechanism mounted on the exterior of a door and a latch strike mounted on the exterior of a door jamb.
FIGS. 1 and 2 depict a "standard" door 10 (i.e., a door having standard 161 circular cut outs for receiving a door knob lock set and not adapted for a mortise lockset, which requires a rectangular cutout in the door trim) employing an internal latching mechanism. FIG. 1 shows the "the door" 10 with knobs 14 located on both sides. Turning either knob 14 will release a latch bolt 16 (FIG. 2) from the door jamb 22 and allow the door 10 to open.
FIG. 2 is a sectional view of the door and knobs of FIG. 1 as seen from plane line 2--2. As shown, the latching mechanism comprises the latch bolt 16, latch bolt tumbler 20, latch control arm 232 and latch control assembly 236. The latching mechanism is predominately located within a noticed portion of the door. The latch bolt 16 extends into a notched section of the door jamb 22 when the door is closed and latched. A deadlocking plunger (not shown) presses against the latch bolt strike 18 and remains substantially within the latch bolt tumbler 20 when the door is in a closed position. Turning either knob 14 causes the latch control assembly 236 to exert a pulling force on the latch control arm 232. This pulling force on the latch control arm 232 draws the latch bolt 16 and deadlocking plunger away from the door jamb 22 and into the latch bolt tumbler 20. With the latch bolt 16 and deadlocking plunger removed into the latch bolt tumbler 20, the door is free to move over the latch bolt strike 18 and swing open.
FIGS. 3 and 4 depict a prior art ("rim" type) panic device. FIG. 3 is a view, partially in section, illustrating the panic device mounted on a door 140. The latching mechanism (comprising a push rail 120, rail assembly 121, latch bolt linkage member 122, latch bolt 124 and latch bolt assembly cover 130) of the panic device is exterior to the door 140. The latch strike 126 is similarly mounted on the exterior of the door jamb 134. When the push rail 120 is pressed toward the door, the resulting movement of the latch bolt linkage member 122 causes the latch bolt 124 to unlatch from the latch bolt strike 126. This permits the door 140 to swing away from the door jamb 134.
FIG. 4 depicts a view from the perspective of one facing the push bar 120. The relative location of the door knob 128 located on the opposite side of the door is depicted with dashed lines. As illustrated, the push bar and the door knob have different vertical alignments, and both the latch bolt 124 and latch strike 126 are visible because they are mounted exteriorly to the door. The door knob 128 is mounted below the push bar 120 so that the door knob is aligned and can be interfaced with a receptacle in the latching mechanism contained in the latch bolt assembly cover 130. This interface between the door knob 128 and the latching mechanism internal to the latch bolt assembly cover 130 allows the latching and unlatching of the latch bolt to be controlled by turning the door knob.
Panic devices of the kind described above typically may be used only with doors and door frames which are specially manufactured or altered for use with a panic device. As discussed above, a door that has been prepared with cutouts generally has a hollow section in which the latching mechanism and door knob are mounted, and a standard door jamb similarly has a hollow section in which a latch strike is mounted. The hollow section and exterior cutouts on a door prepared for a standard two-knob assembly are larger and located at a different vertical height than the hollow section and exterior cutouts on doors prepared for receiving a panic device. The exterior cutouts and the hollow section of a standard two-knob door occupy areas to which fastening screws would be anchored if a conventional panic device were mounted to the door. The location of the exterior cutouts and the size of the hollow area of a standard door preclude a conventional panic device from being securely mounted to a standard two-knob door at the appropriate height. Furthermore, the hollow area of a door jamb is superfluous when an exterior mounted latch strike is mounted to the door frame. This incompatibility between panic devices and "161 doors" and door jambs makes the conversion between conventional latching mechanisms and panic devices an expensive task. When a conventional latching mechanism is replaced with a panic device, it is necessary to replace the entire door and refit the door jamb with a new latch bolt strike. Similarly, when a panic device is replaced with a standard, non-panic latching mechanism, it is necessary to replace the entire door and refit the door jam with a new door strike. Therefore, consumers who convert from a standard knob or handle arrangement of a "161 door" to a panic device, or vice versa, are forced to expend large amounts of time, labor, and money in the conversion. Furthermore, retailers of doors and door finishing parts must keep an inventory of very similar but incompatible stock.